It is being investigated in a 3GPP (3rd Generation Partnership Project) to cause radio terminals to measure/report information conventionally collected by drive-tests or information similar hereto so as to reduce operation cost (OPEX) that is needed for the drive-tests (Drive-Test) to be performed by operators (Non-patent literature 1). The final goal of this investigation is to minimize execution of the drive-tests (Minimization of Drive-Tests: MDT. It is also called a substitute for the drive test (Drive Test Substitution)). In the feasibility study of the MDT, how the radio terminals are caused to measure the information and how the radio terminals are caused to report a log of the measurement results and the past measurement results are being discussed. Currently, the periodical reporting technique and the event triggered measurement reporting technique are specified. Additionally, what is herein called “the measurement” by the radio terminal also includes an operation of “detecting” some situations.
In the periodical technique, a radio network (for example, a radio base station) previously notifies a measurement interval and/or a report interval to the radio terminal, and the radio terminal performs the measurement and/or the reporting according hereto. Herein, as the periodic measurement, there exist the periodical quality measurements of the downlink pilot signals (Periodical downlink pilot measurements).
In the technology of the Non-patent literature 1, the radio terminal periodically performs the received quality measurement of the downlink pilot signals of serving cells (Periodical downlink pilot measurement), and periodically reports the measurement result. Herein, the so-called received quality measurement of the pilot signals is equivalent to measuring RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), CPICH RSCP (Common Pilot channel Received Signal Code Power), CPICH Ec/No (Ec: received energy per chip, No: Noise power density), and the like.
The details of the Non-patent literature 1 will be explained with 3GPP LTE (Long Term Evolution) exemplified by referencing FIG. 20.
The radio terminal (UE: User Equipment) notifies a function the radio terminal itself supports to the radio base station (eNB: enhanced Node B) (UE capability report).
An upper station (EPC: Evolved Packet Core, for example, NM: Network Manager), out of the radio networks, notifies a measurement policy (Measurement policy) to the eNB (Policy indication), and the eNB gives an instruction for the measurement and the reporting to the UE according to the above policy (Measurement logging and reporting configuration). Herein, it is assumed that the measurement and the reporting are performed at an interval T1 and at an interval T2, respectively.
The UE performs the received quality measurement of the downlink pilot signals (for example, the RSRP) and the positioning at the interval T1, maintains the measurement and the measurement result as a log (Logging), and reports the above log to the eNB at the interval T2 (Measurement report). In addition, the eNB reports the report coming from the UE to the upper NW (log report).
Hereinafter, likewise, the UE repeats a series of the operations of the measurement/positioning-the logging-the reporting.
Herein, for determining a lapse of the interval T1/T2, for example, a timer is used. Further, the UE finishes the above series of the operations when the UE is instructed to do so, for example, by the eNB.
Additionally, in some cases, for not only a serving cell but also a neighboring cell, the received quality measurement of the downlink pilot signals is performed periodically.
On the other hand, in the event trigger technique, the radio network (for example, the radio base station) previously notifies the condition, being a trigger for the measurement and/or the reporting, to the radio terminal, and the radio terminal performs the measurement and/or the reporting when the above condition is satisfied. Herein, the condition, being the trigger, includes, for example, a broadcast channel reception error (Broadcast Channel Failure), a paging channel reception error (Paging Channel Failure), the received quality of the serving cell becoming worse than a predetermined threshold (Serving Cell becomes worse than threshold), extra transmit power being less than a predetermined threshold (Transmit power headroom becomes less than threshold), a failure of a random access (Random access failure), and the like (Non-patent literature 2). Additionally, the radio terminal reports information of the time as well responding to a necessity when the trigger has occurred together with the measurement result.
In addition, the radio terminal having a positioning function is instructed to perform the positioning as well periodically or a time point when the trigger has occurred, and to report location information.
In the technology of the Non-patent literature 2, the radio terminal performs the measurement (and the positioning) when the event is triggered, stores the result of the measurement (and the positioning) as the log, and reports it when the event is triggered. Herein, it is assumed that the condition under which the trigger of the measurement occurs is the paging channel reception error (Paging Channel Failure), and the radio terminal performs the received quality measurement of the downlink pilot signals of the serving cell at this time. Further, it is assumed that the condition under which the trigger of the reporting occurs is a time point when a predetermined amount of the logs have been accumulated, and the radio terminal reports the log to the radio network at this time.
The details of the technology of the Non-patent literature 2 will be explained with the 3GPP LTE exemplified by referencing FIG. 21.
The UE notifies functions the UE itself supports to the eNB (UE capability report).
The EPC (for example, NM) notifies a measurement policy (Measurement policy) to the eNB (Policy indication), and the eNB gives an instruction for the measurement and the reporting to the UE according to the above policy (Measurement logging and reporting configuration). Herein, it is assumed that the trigger of the measurement is the paging channel reception error, and the trigger of the reporting is a time point when the amount of the logs (a memory capacity of the terminal used for the logs) has reached a predetermined value.
The UE periodically receives the paging channels, performs the received quality measurement (for example, the RSRP) of the downlink pilot signals of the serving cell and the positioning thereof according to the above instruction when the paging channel reception error (Paging Channel Failure) occurs, and maintains the measurement result and the positioning result together with the time of the occurrence of the paging channel reception error as the log (Logging). And, when the amount of the logs has reached a predetermined value, the UE reports the above logs to the eNB (Measurement report). In addition, the eNB reports the report coming from the UE to the upper NW (Log report).
Hereinafter, likewise, the UE repeats a series of the operations of the measurement/positioning-the logging-the reporting.
Herein, the UE finishes the above series of the operations when the UE is instructed to do so, for example, by the eNB.
Additionally, in some cases, for not only the serving cell but also the neighboring cell, the received quality measurement of the downlink pilot signals when the trigger of the measurement occurs is performed periodically.